Studies On The Fused Deposition Modeling's Quality Control

Since over ten year's development in Rapid Prototyping (RP) technology,there have been more than 10 kinds of processes in application today.With the deeper research work have been doing in this field,more and more people feel unsatisfactory with only manufacturing concept parts by RP technology.How to improve its forming quality and enhancing the application properties of the prototypes is becoming a certain trend of RP technology.FDM is one of the most typical processing methods in RP technology.The factors influencing the FDM forming quality are very complicated,including many problems with heat transfer,viscosity and elasticity theory,polymer material,etc.In this paper,some problems about forming quality are studied.First was the lagging of the nozzle when start and stop.Based on theoretical and experimental analysis,the compensation and advanced control of starts and stops are put forward.Some fail situations lie in starts and stops compensation are also analysed and advanced prevented.Secondly,the anasyses of the forming quality's control are carried out,which including forming accuracy,shrinkage conpensation and bond quality.(1)The correct compensation of the prototype must include two parts:the contour compensation and the shrinkage compensation.The computing formula of compensation is given according to the section and material shrinkage.(2)Based on the characteristics which different to the other Rapid Prototyping technics,the cause of the shrinkage between layers and the shrinkage of the inner polyer.The parameters affect the shrinkage are the numbers of the layers(n),the length of the forming plane(L),the linear shrinkage ratio of material(α),the environment temperature of processing room(θe)and the vitrification temperature of the polymer(θg).We can control the shrink in technics and material.(3)Perfect bond strength can be got in a certain temperature.Pore diameter of nozzle and the thinkness of layer have some effect on the bond strength.The bond strength rises as the thinkness of layer reduce.It's easier to control the flow of the material when the pore diameter of nozzle is reducing.In the end,the improvement of the nozzle structure is proposed after the analysis of the lagging of the starts and stops and bond quality,which aim to better the quality of the quality in hardware.